This invention relates to a method and apparatus for producing dental crowns and bridges by the electrophoretic application of a layer of base mass on a rustproof base article, such as a noble metal nickel alloy.
Dental crowns and bridges customarily comprise a metallic base blank of a noble or non-noble metal alloy, on which layers or strata of dentin and cutting mass are applied in the visible surface areas of the teeth to outwardly create the appearance of natural teeth.
The application of the non-metallic layers onto the base blank has hitherto been an expensive manual process in dental engineering. The base blank is first washed in acetic acid ethyl ester and then rinsed with distilled water. A first layer of base mass is then applied manually with a brush, and solidified by firing in a vacuum furnace, after which a second layer of base mass is brushed on and fired. Next a layer of dentin and cutting mass is applied with a brush onto the layers of base mass and fired in the vacuum furnace, after which at least one additional dentin or cutting mass layer is so applied. After solidification the workpiece is shaped by surface grinding or the like, color-masses are brushed on at certain places, and a final polish firing takes place.
The superposed layers of dentin and cutting mass are anchored onto the metallic base blank via the base mass layers. It is essential that the base mass be applied to form a very thin and uniform layer, which requires considerable manual effort and skill.